The answer, of course, lies in where your audiences are--and where your social media base is. For example, my company's social media base is its blogs, and my social pages serve to amplify that content base where my audiences are. But it's not always easy to decide where your audience will find you, especially with popular new networks cropping up.
How many pages does your company have? Where are they and why are they in those places? Share your thoughts in the comments.